A well-known technique for transporting perishable goods by truck trailer is to use moveable bulkhead units to divide the trailer into separate storage compartments and to maintain each compartment at a temperature necessary to preserve the goods during transport. As an example, truckers are frequently required to carry frozen goods, refrigerated goods and non-refrigerated, or "dry" goods on a single trailer for delivery to a number of different stops. Compartments must then be configured to provide storage spaces maintained at sub-freezing, cooling and ambient temperatures, and must be arranged to allow the trucker access to the compartments to off-load ordered goods at each stop. Preferably, the bulkhead units are repositionable to allow the trucker to adjust the sizes of the individual compartments to meet the load volume and variety for each day's deliveries. Size adjustment is important in maintaining cooling efficiency and economy: a compartment that is only partially filled requires the refrigeration unit to work much harder to keep the stored goods at the right temperature.
Keeping loads at "safe" temperatures sometimes means protecting the loads from ambient temperatures as well as allowing temperature-controlled air to refrigerate the compartments. For example, during winter months, dry goods may need to be protected from freezing and one way to provide such protection is to use thermally-insulated and repositionable bulkhead units to construct a temporary compartment around such goods until they have been safely delivered. It may also be necessary at times to erect temporary insulating shelters for goods that must be protected until used as, for example, frozen meats intended to be handled and served at a fair, festival and the like. Lightweight repositionable insulating bulkhead units make it possible to turn otherwise unrefrigerated interior space into temporarily insulated storage space.
A preferred use for repositionable insulating bulkhead unit is in refrigerated truck trailers, and it is this use that will form much of the disclosure of the present invention. One such bulkhead is described in U.S. Pat. No. 5,010,943 (Boyer) as having a frame within which panels of polystyrene insulation are positioned, a number of reinforcing ribs placed in between adjacent polystyrene panels, a flexible insulating material covers the polystyrene panels and the frame members, a layer of acrylonitrile-butadiene-styrene ("ABS") and resilient seals which extend along the top and down both sides of the frame. The panel is sized to extend across the entire width of a truck trailer and the seals are designed to allow the Boyer panel to be "wedged" against the sidewalls of the trailer to hold them in place.
Boyer also describes a variation of the panel in which first and second panels are used, each equal in size to about one-half the trailer width. The panels interengage along one edge to form an equivalent of the large panel. No provision is made to combine Boyer's panels into other configurations.
Use of bulkheads to divide a refrigerated truck trailer into separate, temperature-maintained zones is described in U.S. Pat. No. 5,161,848 (Lutton), assigned to Kidron, Inc. Lutton describes the advantages of dividing a truck trailer lengthwise using a continuous bulkhead held in floor and ceiling channels formed down the center of the trailer and the use of transverse bulkhead sections to divide the trailer further into frozen, refrigerated and dry zones. One of the advantages claimed by Lutton is ease of access to the individual compartments from the rear door of the trailer, obviating the need for a side door to load and unload.
Lutton describes repositionable bulkhead or partition units used to change the interior trailer configuration having an inner core of conventional insulating material sandwiched between two sheets of lightweight, flexible materia such as fiberglass. Each panel is closed off at its ends by "sealing structures" described as rigid, aluminum tongues sized to be inserted into a channel formed by a U-shaped fiberglass member. The seal formed by the panels is dependent upon the force with which the tongue is forced into and held within the channel. Lutton teaches the use of a foam rubber channel insert as a contact material for the tongue. As seen in FIG. 8 of Lutton, the sealing contact between adjacent panels appears to be confined to the area at which the tongue (110) touches the foam rubber insert (116), while the strength of the panels appears to be limited by the selection of materials used for the panels and the channels.
Lutton also teaches the use of transverse bulkhead panels with edges formed from foam rubber covered by flexible fabric. The bulkhead panels are sized to form a friction fit between the ceiling and floor of the trailer, and between the sidewall of the trailer and the panels used to form the center partition, and the flexible seals are intended to hold the bulkhead panel in place frictionally. Straps are also used to attach the bulkhead panels to special connectors attached to the center panels and to tracks specially installed along the trailer sidewall.
Sites are commonly provided on the faces of such panels for mounting hardware such as handles and tie-down cleats and typically the locations for these sites will be determined prior to molding or forming the panel faces and will be selected to place the handles or tie-downs back-to-back on opposite sides of the panel in order to allow the handles/cleats to be secured by bolts passing through a handle or cleat on one side of the panel, through the panel itself and through the handle or cleat located on the opposite side of the panel. Such sites are desirably recessed so that the handle or cleat does not protrude and interfere with the stacking of cargo. This system works well for initial construction but causes problems when a handle or cleat must be moved to a different location because of configuration problems or damage to the panel.
Accordingly, the need exists for improved durable, lightweight interengageable insulating panels adapted to be assembled within an enclosed space to divide the space into different temperature zones.
Further, the need exists for such panels to be constructed with oversized bottom rails to protect the lowermost portions of the panels and the fasteners used to assemble the rails to the panels.
The need further exists for such panels to allow the flow of air past cartons or other containers that may be stacked up against the panels.
Finally, a need also exists for such panels to provide recesses allowing the selective positioning of handles and cleats on the panels.
The present invention resides in a unique panel unit construction particularly useful for assembly into a center dividing wall down the length of a truck trailer with each panel including reinforcing bottom and side rails made from particularly durable materials and configured to protect the fasteners used to assemble the panels. A series of reinforcing and ventilating channels are formed on the panel faces to stiffen the panels, provide air circulation past goods stacked up against the panels and to provide selectable mounting sites for handles and cleats. Each panel unit is assembled from a pair of spaced-apart face panels glued or otherwise fastened together about their peripheries and between which is injected a closed-cell foam to provide support and insulation. Side rails are mounted to each panel unit with mating male and female connectors to enable the panels to be laterally interengaged. A centrally-positioned track located on the lowermost part of the bottom rail is inserted into a groove formed in the truck floor and a compression seal mounted to the top edge of the panel is compressed against the truck roof to hold the panel in place.